To make the crepes: In a blender, add eggs, milk, sugar, Kerrygold Irish cream, flour and salt. Blend until smooth. Pour into a large bowl and chill in the refrigerator at least 1 hour or overnight.
Heat a 10-inch nonstick skillet over medium heat and brush lightly with butter. Ladle a scant 1/3 cup of batter into the skillet and swirl to coat the bottom of the pan. Cook until bubbles form on the surface, the edges just begin to turn light brown and the top looks almost set, about 2 minutes. Carefully slide a rubber spatula under the crepe and gently flip, using your fingers if needed. Cook 1 minute more. Remove to a sheet tray. Continue cooking the remaining batter until you have between 20 to 25 crepes. Let crepes cool completely before assembling.
To make the filling: Add the butter to a stand mixer fitted with a paddle attachment and beat until creamy and smooth. Add the confectioners’ sugar one cup at a time and beat until smooth. Add the Irish cream and dulce de leche and beat until combined.
To assemble: Place one crepe in the center of a platter. Spread about 1/4 cup filling over the top then place another crepe over the top. Repeat the process until you have used all the crepes and filling and end with a bare crepe on top. Chill for 1 hour.
Dollop the cake with whipped cream and swirl decoratively. Sprinkle with cinnamon for garnish.
Note: Can make crepes and filling 1 day ahead. Batter can be made 2 days ahead.